What is the name of #Ni_3(PO_4)_2#?
Nickel (II) phosphate or simply nickel phosphate.
If we have
We know the anion - that is, the negatively charged species - is phosphate, and we know the name and the charge of the metal.
IUPAC rules say nomenclature of simple salts with cationic metals (salts with only one cation and one anion) goes like
So the name is
If you're more savvy with chemistry, you know that most of the time you'll be working with nickel, it'll only be in that charge. While there are compounds with
(Note that you can't do that with salts that have metals like Iron or Mercury, which commonly appear in more than one charge)